Due to the rising cost of liquid fuel (e.g. diesel fuel) and ever increasing restrictions on exhaust emissions, engine manufacturers have developed dual-fuel engines. An exemplary dual-fuel engine provides injections of a low-cost gaseous fuel (e.g. natural gas) through air intake ports of the engine's cylinders. The gaseous fuel is introduced with clean air that enters through the same intake ports and is ignited by liquid fuel that is injected separately during each combustion cycle. Because a lower-cost fuel is used together with liquid fuel, cost efficiency may be improved. In addition, the combustion of the gaseous and liquid fuel mixture may result in a reduction of harmful emissions.
An exemplary dual fuel engine is disclosed in U.S. Pat. No. 5,035,206 that issued to Welch et al. on Jul. 30, 1991. In particular, the '206 patent discloses a dual-fuel engine having an injector for injecting natural gas into its cylinders to mix with separately-injected diesel fuel. A quantity of natural gas is injected through a delivery conduit into each cylinder at a time when an associated piston uncovers an end of the delivery conduit.
In some dual-fuel applications, especially with two-stroke dual-fuel engines, gaseous fuel injectors can experience leakage through their nozzles. For instance, after injection, a quantity of gaseous fuel may still remain inside the nozzle, and a portion of the gaseous fuel can escape from the nozzle as a result of low pressure areas surrounding the nozzle. This leaked gaseous fuel can slip into an air box of the engine and/or slip into the combustion chamber prematurely and be exhausted through exhaust ports of the engine's cylinder. In these situations, the leaked gaseous fuel does not contribute to the combustion process, resulting in poor fuel efficiency and costly fueling losses.
The disclosed fuel system is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.